Emerald ash borer detected in the Arboretum

Emerald ash borer (photo by Debbie Miller, USDA Forest Service)

The Massachusetts Department of Conservation and Recreation (DCR) and the Department of Agricultural Resources (DAR) have confirmed the detection of emerald ash borer (EAB) in Boston and Suffolk County, following the discovery of the invasive insect at the Arnold Arboretum on July 16. A single adult beetle was spotted during a routine check of monitoring traps deployed in the Arboretum landscape as part of a cooperative detection effort with DCR.

A native to Asia, EAB is a small, metallic green beetle that affects trees in the genus Fraxinus, commonly known as the ashes. In its larval stage, EAB feeds on the conductive tissues of ash trees, disrupting the flow of nutrients and water. In winter, larvae relocate to the bark, further depriving the tissues, and over the course of a number of years this process results in the death of infested trees. Of the Arnold Arboretum’s 15,000 accessioned plants, it holds a Fraxinus collection numbering 175 individual trees across some 100 accessions, comprising approximately 20 species from North America, Asia, and Europe. In coordination with officials from the City of Boston, the Commonwealth of Massachusetts, and the federal government, the Arboretum will follow a recommended control regime for the pest, slowing its spread to other areas and protecting valued specimens in the collection.

“The recent and successful efforts to rid Boston of the Asian longhorned beetle (ALB) demonstrated what a strong cooperative effort can achieve when our canopy is threatened,” said William (Ned) Friedman, Director of the Arnold Arboretum. “Unlike ALB, which was found early and could be eradicated from the area, emerald ash borer has been in North America since 2002 and is now established from the Midwest to the Northeast [see map (pdf)]. Its arrival in Boston has been expected for some time, and so we have a plan in place to minimize our losses and safeguard our fine collection of ash trees.”

EAB was first discovered in North America in the Detroit area in 2002, and probably arrived via solid wood packing material used to ship cargo. Over the past decade, the beetle has decimated ash populations across the Midwest and Mid-Atlantic states, causing millions of dollars of costs for treatment, removal, and replacement of infested trees. The beetle was detected in western Massachusetts in the town of Dalton in August 2012, and was subsequently found in North Andover in Essex County in 2013. Since then, the Arboretum has taken a proactive role in readying for the arrival of EAB, including partnering with DCR to place detection traps in the Arboretum landscape. It was only through regular monitoring and baiting of these traps that the insect was discovered here.

Ash trees represent a significant part of the hardwood forest in New England and are particularly common in western Massachusetts. In urban and managed landscapes, ashes are often planted as street trees. In the City of Boston, green ash represents about 6% of the total urban tree canopy, and in some areas like Dorchester they account for twice that percentage. Commonwealth conservation and agriculture officials are working with the US Forest Service and the Animal and Plant Health Inspection Service (APHIS) of the US Department of Agriculture to undertake steps aimed at slowing the spread of EAB. These include defining a quarantine area to control the movement of specified wood products; conducting a delimiting survey to help identify the extent of the infestation; coordinating with stakeholders for the proper treatment or disposal of infested trees and materials; and maintaining a ban on bringing firewood into state parks and forests.

“Although EAB was first detected in Boston in the Arboretum landscape, we don’t know how long the pest has been in Boston or the extent of its spread yet,” said Andrew Gapinski, Manager of Horticulture. “That the Arboretum was the first to detect EAB in Boston speaks to our coordination with DCR and our ongoing effort to monitor for such pests. Now that we know it’s here, we’re working with state and federal authorities to incorporate EAB into our integrated pest management program. EAB is certainly a destructive pest, but its potential for affecting our collections is comparable to a host of other exotic pests—from winter moth to hemlock wooly adelgid and Dutch elm disease—that we are already dealing with in our changing environment.”

Officials request that Massachusetts residents familiarize themselves with signs of EAB damage, including small, D-shaped exit holes in ash bark, dieback in the upper portions of the tree canopy, and sprouting of branches below dieback occurrences. In winter, severe woodpecker activity at the base of the canopy or on the main stems of ash trees may indicate EAB infestation and should be reported immediately to official forest health personnel. DCR and APHIS will be scheduling EAB information sessions in Suffolk County in early September to provide outreach support to the community on this pest and control efforts. To learn more or to report suspicious tree damage or insect sightings, visit the website of the Massachusetts Introduced Pests Outreach Project, or call the toll-free EAB hotline, 1-866-322-4512.